This invention relates to an image display and pick-up apparatus comprising a screen with controllable transmissivity.
Such apparatus, which can be used in a so-called videophone or for video conference meetings, is known, for example, from the German Patent Publication No. DE 3623029 A1.
As shown in FIG. 6, the conventional image display and pick-up apparatus 10 comprises an image projecting section 12 and an image pick-up section 13 which are both arranged behind a screen 11. When an image is displayed to a user 14, the screen 11 is in a light scattering condition (blurring condition), so that an image from the section 12 and projected on the rear side of screen 11 becomes visible. When an image of the user 14 is to be taken, the screen 11 is brought to a light transmitting condition so that light from the subject 14 can reach the image pick-up section 13.
When using such apparatus in a videophone, it is possible to establish an eye contact between the user 14 and another user via a telephone line.
The conventional image display and pick-up apparatus has the disadvantage that, even if the screen 11 is in the light transmitting condition, the signal light from section 12 is not fully transmitted by the screen 11, but part of this light is reflected by the rear surface of the screen and can reach the image pickup section 13 as indicated by two dot-and-dash lines in FIG. 6. This reflected light interferes with the light from the subject 14 passing through the screen 11, so that a disturbance, in the form of a spot 16, appears in the image 15 picked up by the image pick-up section 13 and displayed at the site of the other user as shown in FIG. 7.